KR20110014717A - Wireless communication method, wireless communication system, and user terminal - Google Patents

Abstract

Each user terminal transmits a data signal to the base station using frequencies of different data transmission bands allocated from the base station, and also transmits a pilot signal to the base station by multiplexing the data signal with the base station. This is disclosed. The resource management unit of the base station determines the pilot transmission band of the user terminal by offsetting some frequency bands of the entire data transmission band for each user terminal so that the pilot transmission band of the user terminal covers the data transmission band of the user terminal. The user terminal is instructed to transmit the pilot signal using the determined frequency of the pilot transmission band.

Description

Wireless communication method, wireless communication system and user terminal {WIRELESS COMMUNICATION METHOD, WIRELESS COMMUNICATION SYSTEM, AND USER TERMINAL}

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a wireless communication method and a base station and a user terminal. In particular, each user terminal transmits a data signal to the base station using a frequency of a different data transmission band allocated from the base station, and transmits a pilot signal. A wireless communication method in a wireless communication system for time-multiplexing a data signal and transmitting the same to a base station, and a base station and a user terminal.

In a wireless communication system such as a cellular system, it is common to perform timing synchronization or propagation path estimation (channel estimation) by using a known pilot signal on the receiving side, and demodulate data based thereon. In addition, in an adaptive modulation scheme that improves throughput by adaptively changing a modulation scheme, a coding rate, or the like according to channel quality, a channel quality, for example, a signal to signal ratio, may be used to determine an optimal modulation scheme or an optimal coding rate. The pilot signal is also used when estimating the interference power ratio SIR (Signal to Interference Ratio).

An orthogonal frequency division multiplexing (OFDM) scheme is a radio access scheme that is resistant to frequency selective fading by multipath in wideband wireless communication. However, OFDM has a problem in that the Peak to Average Ratio (PAPR) of a transmission signal is large, and is not suitable as an uplink transmission method in view of the power efficiency of the terminal. Therefore, in 3GPP LTE, which is the next generation cellular system, single carrier transmission is performed as an uplink transmission method, and frequency equalization is performed on the receiving side (Non Patent Literature 1). Single carrier transmission means multiplexing transmission data or pilot signals only on the time axis, and it is possible to significantly reduce the PAPR as compared to OFDM multiplexing data or pilot signals on the frequency axis.

Single carrier transmission

23 is a frame format example of single carrier transmission, and FIG. 24 is an explanatory diagram of frequency equalization. The frame is time-division-multiplexed with data data consisting of N samples and a pilot pilot. In FIG. 23, two pilot blocks are inserted in one frame. In frequency equalization, the data / pilot separation unit 1 separates the data data and the pilot pilot, and the first FFT unit 2 performs FFT processing on the N sample data to generate N frequency components to generate the channel compensation unit. Enter in (3). The second FFT unit 4 performs an FFT process on the N sample pilots to generate N frequency components, and the channel estimator 5 uses the N frequency components and the N pilot components of the known pilot for each frequency. The channel compensation signal is estimated and input to the channel compensation unit 3. The channel compensator 3 multiplies the N frequency components output from the first FFT unit 2 by the channel compensation signal for each frequency, and the IFFT unit 6 performs IFFT processing on the N channel components compensated for the channel. To convert it to a time signal and output it.

ㆍ CAZAC Series

When frequency equalization is performed at the receiving side in single carrier transmission, in order to accurately perform channel estimation in the frequency domain, the pilot signal has a constant amplitude in the frequency domain, that is, the autocorrelation of any periodic time shift is 0. It is preferable. On the other hand, it is preferable that it is constant amplitude also in a time domain from a PAPR viewpoint. As a pilot sequence that realizes these characteristics, there is a Constant Amplitude Zero Auto Correlation (CAZAC) sequence, and in 3GPP LTE, it is determined to apply this CAZAC sequence as an uplink pilot. Since the CAZAC series has ideal autocorrelation characteristics, it is orthogonal to each other in a circular shift from the same series. In 3GPP LTE, a method of multiplexing pilot signals of different users or pilot signals of different antennas in the same user using different CAZAC sequences has a code division multiplex (CDM).

Zadoff-Chu series, which is a typical CAZAC series, is represented by Equation 1 (Non-Patent Document 2).

Here, k and L are mutually small and represent a series number and a series length, respectively. n is a symbol number, q is an arbitrary integer, L% 2 is the remainder when L divided by 2, and it may be described as Lmod (2). Prime factorization of L

(Gi is a prime number), the number of natural numbers φ (L) smaller than L and the prime L, that is, the number of series of the CAZAC series is

Is given by Specifically, when L = 12, since L = 12 = 2 ² × 3 ¹ , g1 = 2, e1 = 2, g2 = 3, e2 = 1, and from equation 3, the series number k of the CAZAC series is 4 do. For this reason, the larger the L and the smaller the prime number, the larger the series number. In other words, when L is a prime number, the series number k of the CAZAC series is (L-1).

ZC _k (nc), which shifts the CAZAC series ZC _k (n) by c, is

Lt; / RTI > Equation 5 below

As shown in Fig. 2, since the correlation R (τ) between ZC _k (n) and ZC _k (nc) becomes 0 at points other than τ = c, the cyclic shift amounts different from the mother series ZC _k (n) having the same series number. The series generated by adding orthogonal to each other.

When the radio base station receives a plurality of pilots multiplexed with the CDM by the cyclic shift, by correlating with the mother series, it is possible to cut the pilot from the peak position. The narrower the interval between the cyclic shifts, the weaker the resistance to misalignment of the multipath and the reception timing is, and therefore, there is an upper limit on the possible multiple numbers. If the multiplying number by the circular shift is P, the circular shift amount c _p to be assigned to the pth pilot is, for example,

It can be determined by (Non Patent Literature 3).

As described above, in the uplink of 3GPP LTE, pilot and data are time-multiplexed and transmitted by SC-FDMA. 25 is a block diagram of an SC-FDMA transmitter, where reference numeral 7 'is a Discrete Fourier Transformer (DFT) of size N _TX , reference numeral 8' is a subcarrier mapping portion, and reference numeral 9 'is an IDFT portion of size N _FFT . , 10 is a cyclic prefix insertion unit. In addition, in 3GPP LTE, in order to suppress the throughput, N _FFT is set to an integer of 2 power and IDFT after subcarrier mapping is replaced with IFFFT.

The process of adding the cyclic shift c to the mother series ZC _k (n) may be either before DFT or after IFFT. When performing after IFFT, a cyclic shift for c × N _FFT / N _TX samples may be performed. Since the processing is essentially the same, a case of performing a shift shift processing before the DFT will be described as an example.

ㆍ Problem with the conventional technology

In order to reduce intercell interference, it is necessary to repeatedly use CAZAC sequences of different sequence numbers as pilots between cells. This is because the greater the number of repetitions, the greater the distance between cells using the same sequence, and thus the less likely the occurrence of serious interference. To this end, it is necessary to secure a large number of CAZAC series, and in view of the nature of the CAZAC series, it is required to make the sequence length L a large prime number. FIG. 26 is a diagram illustrating interference between cells, and when the number of CAZAC sequences that can be used is 2 as shown in (A), serious interference of the pilot occurs because CAZAC sequences having the same sequence number are used between adjacent cells. In addition, as shown in (B), when the number of CAZAC series is 3, the CAZAC series of the same series number is not used between adjacent cells, but since the number of repetitions is small, the distance between cells using the CAZAC series of the same series number is It is short and there is a high possibility of interference. As shown in (C), when the number of CAZAC sequences is 7, the number of repetitions increases to 7, so that the distance between cells using the CAZAC series having the same sequence number increases, and the possibility of interference gradually decreases.

By the way, in 3GPP LTE, as shown in Fig. 27A, the number of occupied subcarriers is set to a multiple of 12, and the pilot subcarrier interval is twice the subcarrier interval of data to increase transmission efficiency. have. In this case, if the sequence length L of the CAZAC sequence is 6, the sequence number k becomes 2, and pilot interference occurs because the adjacent cell uses the CAZAC sequence of the same sequence number. If the sequence length L is 5, k is 4, but there are still few, and as shown in FIG. 27B, a subcarrier of data not covered by the pilot is generated, resulting in deterioration of channel estimation accuracy.

Therefore, it is conceivable to secure a sufficient sequence length by transmitting a pilot signal transmission band wider than a data transmission band (3GPP R1-060925, R1-063183). 28 shows an example in which the number of multiple pilot signals is two. If the sequence length L is 12, only four CAZAC sequences can be taken, resulting in large inter-cell interference (k = 4). Therefore, series length L is made into 11 prime numbers. When L = 11, ten CAZAC sequences are taken (k = 10), and intercell interference can be reduced. In addition, series length L cannot be 13 or more. The reason is that if it is 13 or more, interference with adjacent frequency bands occurs.

Pilot signals of different users are multiplexed onto the CDM by a circular shift. That is, the user who performed the circuit shift c1 to L = 11 CAZAC series ZC _k (n) is used as the pilot of the user 1, and the user who performs the circuit shift c2 to the CAZAC series ZC _k (n) is used as the pilot of the user 2.

However, in the case where L = 11 CAZAC series ZC _k (n) is cyclically shifted and used for users 1 and 2, as shown in FIG. 28, in user 1 and user 2, the transmission frequency band of the pilot and the transmission frequency of data are used. Since the relative relationship between the bands is different, the channel estimation precision is different. That is, the subcarriers 23 and 24 of the transmission frequency bands of the user 2's data deviate from the pilot transmission frequency bands, and the channel estimation accuracy to the subcarriers deteriorates.

In FIG. 28, the pilot subcarrier interval is twice the data subcarrier interval based on the current 3GPP LTE specification, but the above problem occurs even if the ratio of the subcarrier intervals is changed.

As described above, it is an object of the present invention to accurately perform channel estimation of data subcarriers that deviate from the pilot transmission frequency band.

Another object of the present invention is to provide a subcarrier assigned to each user, even when a predetermined sequence (for example, a CAZAC series ZC _k (n)) having a different amount of cyclic shift is used as a pilot for multiplexing users. The channel estimation can be performed with high accuracy.

Another object of the present invention is to enable channel estimation by separating the pilot of each user by a simple method even when a pilot of multiplexing users uses a different amount of cyclic shift to a given CAZAC sequence.

Another object of the present invention is to improve the channel estimation accuracy of the data subcarrier even if the user has a bad propagation path situation.

Non-Patent Document 1: 3GPP TR25814-700 Figure 9.1.1-1

Non-Patent Document 2: B.M. Popovic, "Generalized Chirp-Like Polyphase Sequences with Optimum Correlation Properties", IEEE Trans. Info. Theory, Vol. 38, pp. 1406-1409, July 1992

Non-Patent Document 3: 3GPP R1-060374, "Text Proposal On Uplink Reference Signal Structure", TI Instruments

<Start of invention>

According to the present invention, each user terminal transmits a data signal to the base station using a frequency of a different data transmission band allocated from the base station, and wirelessly transmits a pilot signal to the base station by time multiplexing the data signal. A wireless communication method in a communication system and a base station and a user terminal.

ㆍ Wireless communication method

In the wireless communication method of the present invention, the frequency band is offset for each user terminal by partially frequency band of all data transmission bands so that the pilot transmission band of the user terminal covers the data transmission band of the user terminal. Each step has a step of determining and a step of instructing the user terminal to transmit a pilot signal using the frequency of the determined pilot transmission band.

The step of instructing the step of calculating the offset amount of the frequency offset and the number of cyclic shifts according to the multiple number of the user terminal for each user terminal, and instructing the user terminal to traverse the CAZAC series pilot signal by the cyclic shift amount; It also has a step of instructing the user terminal to frequency offset the pilot signal by the frequency offset amount.

When the base station multiplexes a plurality of pilot signals transmitted from a plurality of user terminals, adding the frequency components of the pilot signals that do not overlap each other, multiplying the replica of the pilot signal by the addition result, and replica multiplication. Converting the result into a time-domain signal, and then separating the signal portion of the predetermined user terminal from the time-domain signal and performing channel estimation.

The wireless communication method of the present invention comprises the steps of acquiring the situation of a radio wave of a mobile station, and preferentially allocating an intermediate band of all the frequency bands as a data transmission band of a user terminal having a poor propagation path situation and notifying the user terminal. I have more steps. Alternatively, the wireless communication method of the present invention further has a step of performing hopping control for periodically allocating an intermediate band and an end band as the data transmission band of each user terminal.

ㆍ base station

The base station of the present invention determines the pilot transmission band of the user terminal by frequency offsetting some frequency bands of the entire data transmission band for each user terminal so that the pilot transmission band of the user terminal covers the data transmission band of the user terminal. And a resource management unit instructing the user terminal to transmit the pilot signal using the determined frequency of the pilot transmission band.

In the base station, the resource management unit includes a cyclic shift amount calculating unit that calculates the cyclic shift amount according to the offset amount of the frequency offset and the number of multiple user terminals for each user terminal, and the pilot signal of the CAZAC sequence by the cyclic shift amount. In addition to instructing the user terminal to circulate, the user terminal has an instruction unit for instructing the user terminal to frequency offset the pilot signal by the frequency offset amount.

The base station further includes a channel estimating unit for estimating a channel for each user terminal, and the channel estimating unit includes a receiver which multiplely receives a plurality of pilot signals transmitted from a plurality of user terminals, and a pilot in which the plurality of pilot signals do not overlap each other. An adder that adds frequency components of the signal portion, a replica multiplier that multiplies the replica of the pilot signal by the addition result, a converter that converts the replica multiplication result into a time domain signal, and a time domain signal of the predetermined user terminal. A separating section for separating the signal portion, and an estimating section for converting the separated time signal into a signal in the frequency domain to estimate the channel.

The resource management section acquires the radio wave condition of the mobile station, preferentially allocates an intermediate band of all the frequency bands as a data transmission band of the user terminal having a poor propagation path condition, and notifies the user terminal. Alternatively, the resource manager executes hopping control for periodically allocating an intermediate band and an end band of the entire frequency band as a data transmission band of each user terminal.

User terminal

The user terminal of the wireless communication system includes a receiving unit for receiving uplink resource information from a base station, and a pilot generating unit for generating a pilot in accordance with the instruction of the uplink resource information, and the pilot generating unit based on the resource information. A CAZAC sequence generator for generating a CAZAC sequence of a predetermined sequence length and a sequence number as a pilot signal, a first converter for converting a CAZAC sequence that is a pilot signal in a time domain into a pilot signal in a frequency domain, and a subcarrier component of the pilot signal A subcarrier mapping unit for mapping the subcarrier based on the frequency offset information included in the resource information, a second transformer for converting the subcarrier mapped pilot signal into a signal in a time domain, and before or before the first conversion After conversion, iteratively shifts the CAZAC series based on the shift amount included in the resource information It is provided with circuit parts of the shift.

1 is an explanatory view of a first principle of the present invention.
2 is an explanatory diagram of a second principle of the present invention;
3 is an explanatory diagram of a third principle of the present invention;
Fig. 4 is an explanatory diagram of a pilot generation process on the transmitting side that realizes a frequency offset for d subcarriers and a circular shift of (c ₂ -s (k, d, L)).
5 is an explanatory diagram of offsets in a subcarrier mapping unit.
6 is an explanatory diagram of channel estimation processing on the receiving side.
7 is an explanatory diagram of a second pilot generation process;
8 is an explanatory diagram of a copy method on the transmitting side.
9 is an explanatory diagram of a second channel estimation process on a receiving side;
10 is a frame configuration diagram.
11 is an explanatory diagram of a pilot separation method.
12 is an explanatory diagram of a third channel estimation process on the receiving side;
13 is a block diagram of a mobile station.
14 is a block diagram of a pilot generation unit.
15 is a configuration diagram of a base station.
16 is a configuration diagram of a channel estimating unit.
Fig. 17 is a configuration diagram of a pilot generator and a channel estimator for performing second pilot generation and channel estimation processing.
18 is a configuration diagram of a pilot generation unit and a channel estimating unit that perform third pilot generation processing and channel estimation processing.
19 is an explanatory diagram of frequency allocation in the case where the multiple number is four.
Fig. 20 is an explanatory diagram for hopping control to switch the transmission band allocated to each user for each frame.
Fig. 21 is an explanatory diagram for hopping control to switch the transmission band allocated to each user for each frame;
22 is a block diagram of a pilot generation unit in the case of hopping control;
23 is an example frame format for single carrier transmission.
24 is an explanatory diagram of frequency equalization.
25 is a configuration diagram of an SC-FDMA transmitter.
Fig. 26 is a diagram illustrating interference between cells.
27 is a first explanatory diagram of a conventional data transmission band and a pilot transmission band.
28 is a second explanatory diagram of a conventional data transmission band and a pilot transmission band.

BEST MODE FOR CARRYING OUT THE INVENTION [

(A) Principles of the Invention

As shown in FIG. 1 (A), CAZAC sequence ZC _k (n) using that subjected to traverse shift c1 as the pilot for a user 1 to the, CAZAC user that subjected to the traverse shift c2 in sequence ZC _k (n) 2 When used as a pilot, as described with reference to FIG. 28, the subcarriers 23 and 24 in the transmission frequency bands of the user 2's data deviate from the pilot transmission frequency bands, resulting in deterioration of channel estimation accuracy in the subcarriers. In Fig. 1, DFTs {ZC _k (n-c1)} and DFTs {ZC _k (n-c2)} respectively perform a cyclic shift c1, c2 to the CAZAC series ZC _k (n) with L = 11. after such a _{ZC k (n-c1),} ZC k is the pilot in the frequency domain obtained by performing a DFT process for (n-c2).

Therefore, as shown in Fig. 1B, when the pilot has a frequency offset in accordance with the data transmission band for each user, the pilot transmission band always covers the data transmission band. In the example of FIG. 1B, the pilot DFT {ZC _k (n-c2)} of user 2 may be offset by one subcarrier.

However, if the pilot DFT {ZC _k (n-c2)} is offset, the correlation between the reception pilot and the replica ZC _k (n) of the known pilot on the receiving side does not become a peak at tau = c2, and the peak position is shifted. Cannot be correctly restored, resulting in no channel estimation. The reason why the correlation peak position is shifted is described below.

ㆍ Relationship of Frequency Offset and Iterative Shift in Time Domain

First, the relationship between the frequency offset and the circular shift in the time domain will be described. If the result of performing the DFT conversion on the CAZAC series ZC _k (n) is F (m), F (m) is

Lt; / RTI &gt; By transforming using the equations (7) and (4),

Is established. D (modL) is the remainder of d divided by L.

As can be seen from Equation 8, applying the cyclic shift c to the CAZAC sequence in the time domain is equivalent to applying a phase rotation with the cyclic shift for d subcarriers in the frequency domain. Since k and L are small to each other, c (<L) is uniquely determined by k and d. Change c = s (k, d, L) to make it easier to understand that c is determined by k, d, and L. Table 1 shows the values of c according to various combinations of s (k, d, L) and k in the case of L = 11. For example, if k = 1, d = 1, L = 11, c = 1, k = 2, d = 1, L = 11, c = 6.

As described above, applying a frequency offset of one subcarrier to the pilot 2 as shown in FIG. 2 (A) is a cycle of one subcarrier in the frequency domain, as shown in FIG. After applying the shift, it corresponds to moving the component p11 in the subcarrier 1 to the subcarrier 12. As a result, from Equation 8, the correlation peak position of Pilot 2 (see Equation 5) is shifted by s (k, d, L) (τ = c2 + s (k, d, L)). Since the correlation peak position of the pilot 1 (τ = c1) does not shift, the correlation peak positions of the pilot 2 and the pilot 1 change by s (k, d = 1, L = 11) relatively, so that the receiver correctly recovers the pilot. As a result, channel estimation is not possible.

Any order as the peak position prior art, the circuit may be changed from the shift amount c ₂ a _{(c 2 -s (k, d} , L)). That is, as shown in Fig. 3A, the pilot 2 has a frequency offset of d subcarriers (d = 1 in the figure) and a circular shift of (c ₂ -s (k, d, L)). If both are added, the relationship between pilots 1 and 2 is as shown in Fig. 3B. In this way, the correlation peak positions of the pilots 1 and 2 do not shift, and the pilot can be correctly restored on the receiving side, thereby improving the channel estimation accuracy. That is, the pilot 1 and the pilot 2 can be separated by the position of the correlation peak value (tau = c1, tau = c2) as before the frequency offset in Fig. 1A.

(a) first pilot generation processing and channel estimation processing

FIG. 4 is an explanatory diagram of a pilot generation process on the transmission side for realizing the frequency offset for the d subcarriers and the cyclic shift of (c ₂ -s (k, d, L)) described in FIG.

The CAZAC series generating section 11 generates, for example, a CAZAC series ZC _k (n) with L = 11 as a pilot, and the cyclic shift section 12 generates a CAZAC series ZC _k (n) with c ₂ -s (k, By sequential shifting by d, L), ZC _k (n-c2 + s (k, d, L)) is generated and input to the DFT unit 13. The DFT unit 13 of the N _TX size (N _TX = L = 11) performs a DFT operation on ZC _k (n-c2 + s (k, d, L)) to generate a pilot DFT {ZC _k (n-c2 + s (k, d, L))}. The subcarrier mapping section 14 offsets eleven pilot components p1 to p11 in the frequency domain by d subcarriers (d = 1 in the figure) and inputs them to the IFFT section 15.

5 is an offset explanatory diagram of the subcarrier mapping unit 14, where (A) is no offset (d = 0), and the subcarrier mapping unit 14 converts the eleven pilot components p1 to p11 into the IFFT unit 15. Frequency f _i , f _{i + 1} , f _{i + 2} ,. , f Enter into the terminal of _{i + 10} and enter 0 into the other terminal. (B) is the case where there is offset (d = 1), and the subcarrier mapping section 14 assigns the eleven pilot components p1 to p11 to the frequencies f _{i + 1} , f _{i + 2} , f _i of the IFFT section 15. ₊₃ ,… , f Enter into the terminal of _{i + 11} and enter 0 into the other terminal. The IFFT unit 15 of the N _FFT size (for example, N _FFT = 128) performs an IDFT operation on the input subcarrier component to convert it into a time domain signal, and the CP (Cyclic Prefix) inserter 16 interferes with the interference. A cyclic prefix for prevention is added and output. (C) is another embodiment in the case of having an offset (d = 1). In this case, the cyclic shift unit 12 cyclically shifts the CAZAC series ZC _k (n) by c ₂ to generate ZC _k (n-c2) and input it to the DFT unit 13. DFT unit 13 performs a DFT calculation process on ZC _k (n-c2) to generate the pilot _{DFT {ZC k (n-c2} )}. The subcarrier mapping section 14 controls the pilot components p2 to p11 to the IFFT sections f _{i + 1} , f _{i + 2} ,. , input to the terminal of f _{i + 10} and the pilot component p1 to the terminal of the IFFT unit f _{i + 11} .

6 is an explanatory diagram of channel estimation processing on the receiving side.

In the channel estimating section, pilot 1 and pilot 2 (refer to FIG. 3B) transmitted from user 1 and user 2, respectively, are multiplexed in the air and subcarrier frequencies f _i , f _{i + 1} , f _{i + 2} , f _{i + 3} ,.. and subcarrier components p1 to p12 of f _{i + 11} are input. The subcarrier adder 52 adds the subcarrier components p12 and p1 not overlapping each other, and makes the addition result a subcarrier component p1 of the subcarrier frequency f1.

The replica signal multiplier 53 multiplies the pilot replica signal (the DFT calculation processing to the known CAZAC series ZC _k (n) having a cyclic shift amount of 0) qi and the received pilot signal pi for each subcarrier, and the IDFT unit Reference numeral 54 performs an IDFT operation on the replica multiplication result and outputs a delay profile in the time domain. Since the delay profile in the time domain is a length L sample, and has a correlation peak at t = c1 and t = c2, the profile extraction section 55 separates the correlation peak at t = (c1 + c2) / 2 so that user 1, Profiles PRF1 and PRF2 of length L / 2 samples for two are generated. The L-size DFT section 56a inserts L / 4 zeros into each of both sides of the profile PRF1 having a length of L / 2 and performs a DFT operation with a length L. Thereby, the subcarrier frequencies f _i , f _{i + 1} , f _{i + 2} , f _{i + 3} ,. , channel estimation values h1 to h11 of user 1 at f _{i + 10} are obtained. Similarly, the L-size DFT unit 56b inserts L / 4 zeros into each of both sides of the profile PRF2 having the length of the L / 2 sample to perform the DFT operation with the length L. Thereby, the subcarrier frequencies f _{i + 1} , f _{i + 2} , f _{i + 3} ,... From the DFT unit 56b are obtained. , channel estimation values h2 to h12 of user 2 at f _{i + 11} are obtained. However, the sub-carriers in the addition section 52 adds the p1 and p12 Since the subcarrier component of subcarrier frequency f _i, the channel estimation value of the subcarrier frequency f _i which is output from the DFT unit (56b) subcarrier frequency f _Let channel estimate h12 of _{i + 11} be.

As described above, if the distortion due to the radio wave condition is small for each of the pilot 1 and the pilot 2, as shown in FIG. Can be separated in the form. If the distortion due to the propagation situation is large, the subcarrier addition may be omitted and separated on the delay profile in the time domain after direct replica multiplication.

(b) second pilot generation processing and channel estimation processing

In the first channel estimation process, subcarrier components p12 and p1 that do not overlap each other are added, and the addition result is regarded as a component of the subcarrier frequency f _i . However, if the carrier component of the subcarrier frequency f _i of the received signal has already been added to p12 and p1, it is not necessary to add the subcarrier at the receiving side.

Fig. 7 is a second pilot generation process explanatory diagram, in which (A) shows data subcarriers of user 1 and user 2;

As shown in Fig. 7B, the transmitting side (user 1) copies the subcarrier component p1 of the subcarrier frequency f _i of the pilot 1 to be a subcarrier component of the subcarrier frequency f _{i + 11} . As shown in FIG. 7C, the user 2 copies and transmits the subcarrier component p12 of the subcarrier frequency f _{i + 11} of the pilot 2 to be a subcarrier component of the subcarrier frequency f _i . As a result, as shown in Fig. 7D, these pilots are multiplexed and received by the receiving side, and the carrier component of the subcarrier frequency f1 of the received signal is a value obtained by adding p1 and p12. The carrier component of the frequency is also a value obtained by adding p1 and p12, so that the subcarrier addition on the receiving side is unnecessary.

8 is a copy method explanatory diagram at the transmitting side, (A) is a copy method of pilot 1 at user 1, and subcarrier mapping section 14 shows that carrier component p1 of subcarrier frequency f _i of pilot 1 is subcarrier frequency f; so also the subcarrier component of the _{i + 11} and input to the frequency f _{i + 11} of the terminals of the IFFT unit 15. (B) is a copying method of pilot 2 in user 2, and subcarrier mapping section 14 performs IFFT such that carrier component p12 of subcarrier frequency f _{i + 11} of pilot 12 is also a subcarrier component of subcarrier frequency f _i . It is also input to the terminal of the frequency f _i of the unit 15. (C) is another embodiment of the copying method of pilot 2 for user 2, and corresponds to FIG. 5C.

9 is an explanatory diagram of channel estimation processing on the receiving side. In the channel estimating section, pilot 1 and pilot 2 (see FIGS. 7B and 7C) transmitted from user 1 and user 2, respectively, are multiplexed in the air and subcarrier frequencies f _i , f _{i + 1} , f _{i + 2} , f _{i + 3} ,... and subcarrier components p1 to p12 of f _{i + 11} are input (FIG. 7D).

The replica signal multiplier 53 for user 1 multiplies the pilot replica signals qi (q1 to q11) and the received pilot signals pi (p1 to p11) for each subcarrier, and then the IDFT unit 54 and the correlation separation unit ( 55) The DFT unit 56 performs the same process as that of FIG. 6 to generate the channel estimation values h1 to h11 of the user 1.

On the other hand, the replica signal multiplier 53 'for user 2 multiplies the pilot replica signals qi (q1 to q11) and the received pilot signals pi (p2 to p12) for each subcarrier, and thereafter, the IDFT unit 54', The correlation separation unit 55 'and the DFT unit 56' perform the same processing as that of user 1 to generate channel estimation values h2 to h12 of user2.

(c) third pilot generation processing and channel estimation processing

In the first channel estimation process, the correlation component 55 separates the pilot component of the user 1 and the pilot component of the user 2, but as shown in FIG. 10, for example, two pilot blocks are included in one frame. If it is, it can be separated as follows. 11 is an explanatory diagram of a pilot separation method, in which (A) shows data subcarriers of users 1 and 2;

User 1 and User 2's first pilot 1 (= DFT {ZC _k (n-c1)}), pilot 2 (= DFT {ZC _k (n-c2 + s (k, d, L)))} As shown in (B) and (C), the subcarrier component is multiplied by +1 for transmission, and as shown in (D) and (E) for each subcarrier component of the next pilot 1 and pilot 2, Multiply by +1 and -1 to transmit.

As a result, the reception side receives the pilot multiple signals of the first or less time.

DFT {ZC _k (n-c1)} × (+1) + DFT {ZC _k (n-c2 + s (k, d, L)) × (+1)

And then the pilot multiple signal of

DFT {ZC _k (n-c1)} × (+1) + DFT {ZC _k (n-c2 + s (k, d, L)) × (-1)

Receive

Therefore, in order to generate the pilot of user 1 on the receiving side, the following pilot multiplexing signal may be added to the first pilot multiplexing signal. That is, since the polarities of pilot 2 are different, pilot 2 is negated by addition and pilot 1 remains. In addition, in order to generate the pilot of user 2 on the receiving side, the following pilot multiplexing signal may be subtracted from the first pilot multiplexing signal. That is, since pilot 1 has the same polarity, pilot 1 is negated by subtraction and pilot 2 remains.

12 is an explanatory diagram of channel estimation processing on the receiving side. In the channel estimating section, pilot 1 and pilot 2 (refer to (B), (C), (D) and (E)) of FIG. 11 transmitted from user 1 and user 2, respectively, are multiplied in the air, and the subcarrier frequency f _i , f _{i + 1} , f _{i + 2} , f _{i + 3} ,. and subcarrier components p1 to p12 of f _{i + 11} are input.

The inter-block subcarrier calculating unit 61 receives and stores the first received pilot signal. Subsequently, when the inter-block subcarrier calculating unit 61 generates the pilot of the user 1, when the second received pilot signal is received, the inter-block subcarrier calculating unit 61 adds the first and second received pilot signals for each subcarrier, thereby subcarrier of the pilot 1 subcarrier. f _i , f _{i + 1} , f _{i + 2} , f _{i + 3} ,... and carrier components p1 to p11 of f _{i + 10} are generated. The replica signal multiplier 53 for user 1 multiplies the pilot replica signals qi (q1 to q11) and the received pilot signals pi (p1 to p11) for each subcarrier, and then the IDFT unit 54 and the correlation separation unit ( 55) The DFT unit 56 performs the same process as that of FIG. 6 to generate the channel estimation values h1 to h11 of the user 1. In addition, although the precision is inferior, the replica signal multiplication result may be taken as channel estimation values h1 to h11.

On the other hand, when the user 2 pilot is generated, the inter-block subcarrier calculating unit 61 subtracts the first and second received pilot signals for each subcarrier, and the subcarriers f _i , f _{i + 1} , f of pilot 2 are generated. _{i + 2} , f _{i + 3} ,... and carrier components p2 to P12 of f _{i + 11} are generated. The replica signal multiplier 53 'for user 2 multiplies the pilot replica signals qi (q1 to q11) and the received pilot signals pi (p2 to p12) for each subcarrier, and then the IDFT unit 54' and correlation separation. The unit 55 'and the DFT unit 56' perform the same processing as that of user 1 to generate channel estimation values h2 to h12 of user2.

In the above, the third pilot generation process and the channel estimation process can be applied even when the number of pilot blocks is 2, but even when the number of pilot blocks is even. In this case, the base station instructs any user terminal to multiply the pilot signal of the entire block by +1, the other user terminal to multiply the half of the pilot signal by +1, and the other half of the pilot signal by -1. Instruct. When the base station multiplexes the pilot signals transmitted from the respective user terminals, the base station performs the addition and subtraction calculation processing to the pilot signals of the entire block so that only the pilot signals from the predetermined user terminals (user terminals 1 or 2) remain. Multiply a replica of the pilot signal by the operation result, converts the replica multiplication result into a time domain signal, and then separates the signal portion of the user terminal from the time domain signal to estimate the channel.

(B) mobile stations

13 is a configuration diagram of a mobile station.

When uplink transmission data has occurred, the mobile station (user terminal) makes a resource allocation request to the base station, and the base station makes resource allocation based on the propagation path state of the mobile station, and notifies the mobile station of resource allocation information. The mobile station transmits the notified data and the pilot. That is, the radio unit 21 inputs the radio signal received from the base station into the received signal baseband processing unit 22 as a baseband signal. The baseband processor 22 separates data and other control information from the received signal, separates resource allocation information, and inputs the resource allocation information to the transmission resource manager 23. The resource allocation information includes, in addition to the data transmission frequency band, timing, modulation scheme, etc., the pilot transmission frequency band, the sequence number and sequence length L of the CAZAC sequence used as the pilot, the cyclic shift amount, the frequency offset amount d, and the like.

The transmission resource management unit 23 inputs information necessary for the data and control information transmission processing to the data processing unit 24 and inputs information necessary for the pilot generation / transmission process to the pilot generation unit 25. The data processing unit 24 performs data modulation and single carrier transmission processing on the data and control information based on the information input from the transmission resource management unit 23, and outputs the pilot generation unit 25 to the transmission resource management unit 23. In accordance with the instruction from the CAZAC sequence, generation of a CAZAC sequence, a cyclic shift, a frequency offset, and the like are performed to generate a pilot, and the frame generation unit 26, for example, as shown in FIG. A time division multiplexing block is used to create a frame and transmit it from the radio section 21 toward the base station.

FIG. 14 is a configuration diagram of the pilot generation section 25, which is a configuration diagram when a pilot is generated in accordance with the first pilot generation process described in FIG. 3, (A) is a configuration diagram when a circuit shift is performed before the DFT, B) is a block diagram in the case where a circuit shift is performed after IFFT.

In FIG. 14A, the transmission resource management unit 23 stores each of the parameters (CAZAC sequence number, sequence length, cyclic shift amount, frequency offset) required for pilot generation and transmission included in the resource allocation information received from the base station. Type in

The CAZAC series generating section 11 generates the indicated series length L, the CAZAC series ZC _k (n) of the series number as a pilot, and the cyclic shift section 12 indicates the c sample portion indicating the CAZAC series ZC _k (n). The ZC _k (nc) obtained by the cyclic shift is input to the DFT unit 13. For example, if it is pilot 1 of FIG. 3B, the circuit shift unit 12 shifts ZC _k (n) by c1 to generate ZC _k (n-c1), and if it is pilot 2, c ₂ − ZC _k (n-c2 + s (k, d, L)) is generated by shifting by s (k, d, L) and input to the DFT unit 13. The DFT unit 13 of size N _TX (N _TX = L) performs a DFT operation on the input pilot ZC _k (nc) to generate a pilot DFT {ZC _k (nc)} in the frequency domain. The subcarrier mapping unit 14 controls the mapping position of the pilot based on the indicated frequency offset amount d to offset the frequency, and the IFFT unit 15 of the N _FFT size (N _FFT = 128) inputs the input subcarrier component. IFFT operation is performed to convert the signal into a time domain signal and input it to the frame generator 26.

FIG. 14B is a configuration diagram of the pilot generation unit 25 in the case where the circuit shift is performed after the IFFT, and the circuit shift unit 12 performs the circuit shift for c × N _FFT / N _TX samples, thereby. The exact same result as (A) is obtained.

(C) base station

15 is a configuration diagram of a base station.

When uplink transmission data is generated, the mobile station (user) executes a procedure of establishing a communication link with the base station, and transmits a radio wave situation to the base station in the process of this procedure. That is, the mobile station receives the common pilot transmitted from the base station and performs radio measurement (SIR or SNR measurement), and reports the radio measurement result to the base station as a radio wave condition. For example, the base station divides the transmission band into a plurality of transmission frequency bands, transmits a common pilot for each transmission frequency band, the mobile station wirelessly measures each transmission frequency band, and sends a measurement result to the base station. When the base station acquires the radio path condition from the mobile station and receives a resource allocation request, the base station allocates resources based on the radio path condition of the mobile station and sends resource allocation information to the mobile station.

The radio unit 31 converts the radio signal received from the mobile station into a baseband signal, the separation unit 32 separates the data / control information and the pilot, inputs the data / control information to the data processing unit 33, The pilot is input to the channel estimator 34. The data processing unit 33 and the channel estimating unit 34 have a frequency equalization configuration shown in FIG.

The data processing unit 33 demodulates the context data by the radio wave transmitted from the mobile station at the time of establishing the communication link and inputs it to the uplink resource management unit 35. The uplink resource management unit 35 performs resource allocation based on the propagation path situation, prepares resource allocation information, and inputs it to the downlink signal baseband processing unit 36. The resource allocation information includes, in addition to the data transmission frequency band, timing, modulation scheme, etc., the pilot transmission frequency band, the sequence number and sequence length L of the CAZAC sequence to be used as the pilot, the cyclic shift amount, the frequency offset amount d, and the like. The downlink signal baseband processor 36 time-division-multiplexes downlink data, control information, and resource allocation information, and transmits them from the radio section 31.

When the mobile station receives the resource allocation information, it performs the processing described with reference to Figs. 13 and 14 to transmit a frame composed of data and pilot.

The channel estimator 34 performs the first channel estimation process described with reference to FIG. 6 using the pilot input separated from the separator 32 and inputs the channel estimate value to the data processor 33. The data processing unit 33 performs channel compensation based on the channel estimate value, and demodulates data based on the channel compensation result. In addition, the uplink resource management unit 35 includes a circulation shift amount calculation unit 35a and a link assignment information indicating unit 35b.

16 is a configuration diagram of the channel estimating unit 34, and the same parts as in FIG.

The DFT unit 51 applies a DFT calculation process to the pilot signal input from the separation unit 32 and converts the pilot signal (subcarrier components p1 to p12) in the frequency domain. The subcarrier adder 52 adds the subcarrier components p12 and p1 which do not overlap each other, and makes the addition result a subcarrier component p1 of the subcarrier frequency f1.

The replica signal multiplier 53 multiplies the pilot replica signal qi by the received pilot signal pi for each subcarrier, and the IDFT unit 54 performs an IDFT operation on the replica multiplication result and outputs a pilot signal in the time domain. The profile extraction unit 55 separates the IDFT output signal at t = (c1 + c2) / 2, and selects the profile PRF1 (see FIG. 6) if it is a received signal from the user 1, and the DFT unit 56 uses the profile. A DFT operation is performed on the PRF1 to output the channel estimates h1 to h11. On the other hand, if the signal is received from user 2, profile extraction section 55 selects profile PRF2, and DFT section 56 performs a DFT operation on profile PRF2 and outputs channel estimates h2 to h12.

(D) second pilot generator and channel estimator

FIG. 17A is a configuration diagram of a pilot generation unit that performs the second pilot generation process described with reference to FIG. 7, and the same portions as those of the pilot generation unit in FIG. 14A are denoted by the same reference numerals. The difference is that the subcarrier mapping section 14 performs two operations of subcarrier mapping based on the frequency offset amount d and copying of the pilot component of the predetermined subcarrier, and the other operations are the same.

The CAZAC series generating section 11 generates the indicated series length L and the CAZAC series ZC _k (n) of the series number as a pilot, and the cyclic shift section 12 includes c samples indicated by the CAZAC series ZC _k (n). The ZC _k (nc) obtained by the cyclic shift is input to the DFT unit 13. For example, if it is pilot 1 for user 1 of FIG. 7B, the circuit shift unit 12 shifts ZC _k (n) by c1 to generate ZC _k (n-c1), and for user 2 If the pilot 2 of, is then shifted by c ₂ -s (k, d, L), ZC _k (n-c 2 + s (k, d, L)) is generated and input to the DFT unit 13. The DFT unit 13 of size N _TX (N _TX = L) performs a DFT operation on the input pilot ZC _k (nc) to generate a pilot DFT {ZC _k (nc)} in the frequency domain.

The subcarrier mapping unit 14 performs subcarrier mapping based on the copy information and the frequency offset information instructed by the transmission resource management unit 23. For example, for the pilot 1 of the user 1 of FIG. 7B, the subcarrier mapping process shown in FIG. 8A is performed, and for the pilot 2 of the user 2 of FIG. 7C, The subcarrier mapping process shown in FIG. 8B is performed. The IFFT unit 15 having an N _FFT size (for example, N _FFT = 128) performs an IFFT operation on the input subcarrier component, converts it into a pilot signal in the time domain, and inputs it to the frame generation unit 26.

FIG. 17B is a configuration diagram of the channel estimating unit 34 that performs the second channel estimation process described in FIG. 9, and the same parts as those of the channel estimating unit of FIG. 16 are denoted by the same reference numerals. The difference is that the subcarrier adder 52 is deleted and the replica signal multiplier 53 multiplies.

The DFT unit 51 applies a DFT calculation process to the pilot signal input from the separation unit 32 and converts the pilot signal (subcarrier components p1 to p12) in the frequency domain. When the replica signal multiplier 53 receives pilot 1 from user 1, the subcarriers f _i , f _{i + 1} , f _{i + 2} , f _{i + 3} , and the like of the received pilot output from the DFT unit 51 are received. … subcarriers f _{i + 1} , f of the received pilot output from the DFT unit 51 when multiplying the components p1 to p11 of f _{i + 10 by} the replica signals q1 to q11 and receiving pilot 2 from user 2 _{i + 2} , f _{i + 3} ,... multiplies the components p2 to p12 of f _{i + 11 by} the replica signal.

The IDFT unit 54 then performs an IDFT operation on the replica multiplication result and outputs a delay profile in the time domain. The profile extraction unit 55 separates the IDFT output signal at t = (c1 + c2) / 2, and selects the profile PRF1 (see FIG. 6) if it is a pilot signal from the user 2, and the DFT unit 56 uses the profile. A DFT operation is performed on the PRF1 to output the channel estimates h1 to h11. On the other hand, if the signal is received from the user 1, the profile extraction unit 55 selects the profile PRF2, and the DFT unit 56 performs a DFT operation on the profile PRF2 and outputs channel estimation values h2 to h12.

(E) third pilot generator and channel estimator

FIG. 18A is a configuration diagram of a pilot generation unit that performs the third pilot generation process described in FIG. 11, and the same parts as those in the pilot generation unit of FIG. 14A are denoted by the same reference numerals. The difference is that the polarity adding section 61 is added, and the other operations are the same.

The CAZAC series generating section 11 generates the indicated series length L and the CAZAC series ZC _k (n) of the series number as a pilot, and the cyclic shift section 12 includes c samples indicated by the CAZAC series ZC _k (n). The ZC _k (nc) obtained by the cyclic shift is input to the DFT unit 13. For example, if it is pilot 1 for user 1 of FIGS. 11B and 11D, the circuit shift unit 12 shifts ZC _k (n) by c1 to generate ZC _k (n-c1). , If it is pilot 2 for user 2, it is cyclically shifted by c ₂ -s (k, d, L) to generate ZC _k (n-c 2 + s (k, d, L)) and input to the DFT unit 13. do. The DFT unit 13 of size N _TX (N _TX = L) performs a DFT operation on the input pilot ZC _k (nc) to generate a pilot DFT {ZC _k (nc)} in the frequency domain.

The subcarrier mapping unit 14 performs subcarrier mapping based on the frequency offset information instructed by the transmission resource management unit 23. The polarity assigning unit 61 gives the polarity instructed from the transmission resource management unit 23 to the output of the subcarrier mapping unit 14 and inputs it to the IFFT unit 15. For example, in the case of pilot 1 for user 1, since the polarity of +1 is indicated in the first and second pilot blocks (see FIGS. 11B and 11D), the polarity assigning unit 61 is a subcarrier. All carrier components output from the mapping unit 14 are multiplied by +1 and input to the IFFT unit 15. In the case of pilot 2 for user 2, the polarity of +1 is indicated in the first pilot block and the polarity of -1 is indicated in the second pilot block (see (C) and (E) in FIG. 11). The granting unit 61 multiplies all the carrier components output from the subcarrier mapping unit 14 by +1 in the first pilot block and inputs them to the IFFT unit 15, multiplies -1 in the second pilot block, and IFFT It is input to the part 15.

The IFFT unit 15 having an N _FFT size (N _FFT = 128) performs an IFFT operation on the input subcarrier component, converts it into a pilot signal in the time domain, and inputs it to the frame generator 26.

FIG. 18B is a configuration diagram of the channel estimating unit 34 that performs the third channel estimation process described with reference to FIG. 12, and the same parts as those of the channel estimating unit of FIG. The difference is that the inter-block subcarrier adding unit 62 is provided in place of the subcarrier adding unit 52.

The DFT unit 51 applies a DFT arithmetic process to the pilot signal of the first pilot block input from the separating unit 32, converts it into a pilot signal (subcarrier components p1 to p12) in the frequency domain, and inter-block subcarrier adding unit. Reference numeral 62 stores the pilot signals (subcarrier components p1 to p12) in the built-in memory. Thereafter, the DFT unit 51 applies a DFT arithmetic process to the pilot signal of the second pilot block input from the separating unit 32, converts the pilot signal (subcarrier components p1 to p12) in the frequency domain, and converts the intercarrier subcarriers. Input to the adder 62.

If the inter-block subcarrier adding unit 62 receives pilot 1 from user 1, the pilot signals (subcarrier components p1 to p12) of the first pilot block stored and the pilot signals (sub) of the second pilot block are stored. Carrier components p1-p12) are added for every subcarrier. As a result, pilot signal components from other multiplexed users (for example, user 2) are removed. In addition, if the inter-block subcarrier adding unit 62 receives pilot 2 from user 2, the pilot signal of the second pilot block (from the pilot signals (subcarrier components p1 to p12) of the first pilot block stored ( Subcarrier components p1 to p12) are subtracted for each subcarrier. As a result, pilot signal components from other multiplexed users (for example, user 1) are removed.

If the replica signal multiplier 53 receives pilot 1 of user 1, the subcarriers f _i , f _{i + 1} , f _{i + 2} , f _i of the received pilot output by the inter-block subcarrier adder 62. ₊₃ ,… subcarrier f _{i +} of the received pilot output from the inter-block subcarrier adder 62 when multiplying the components p1 to p11 of f _{i + 10 by} the replica signals q1 to q11 and receiving pilot 2 of user 2 ₁ , f _{i + 2} , f _{i + 3} ,... , the components p2 to p12 of f _{i + 11} and the replica signals q1 to q11 are multiplied.

The IDFT unit 54 then performs an IDFT operation on the replica multiplication result and outputs a pilot signal in the time domain. The profile extraction unit 55 separates the IDFT output signal at t = (c1 + c2) / 2, and selects the profile PRF1 (see FIG. 6) if it is a pilot signal from the user 1, and the DFT unit 56 uses the profile. A DFT operation is performed on the PRF1 to output the channel estimates h1 to h11. On the other hand, if the signal is received from user 2, profile extraction section 55 selects profile PRF2, and DFT section 56 performs a DFT operation on profile PRF2 and outputs channel estimates h2 to h12.

(F) adaptive control

As described above, the uplink resource management unit 35 (FIG. 15) from the base station is based on the propagation path conditions of the mobile station, and the pilot transmission frequency band, the CAZAC sequence number and sequence length L, the cyclic shift amount, the frequency offset d, and the like. Determine and notify the mobile station. The uplink resource manager 35 of the base station also determines the number of multiples in the transmission frequency band based on the propagation path situation of each mobile station.

Fig. 19 is an explanatory diagram of frequency allocation in the case where the multiple number is 4, the first 12 subcarriers are assigned to user 1, the second 12 subcarriers are assigned to user 2, and the third 12 subcarriers are assigned to user 3; The carrier is assigned and the last 12 subcarriers are assigned to the user 4, and the CAZAC series ZC _k (n) having a sequence length L = 19 is used as a pilot of each user by varying the cyclic shift amount.

The frequency offset of the pilot is set to cover as much as possible the data transmission bandwidth of each user. The circular shift calculation unit 35a (Fig. 15) calculates the circular shift amount of each user by the following equation.

Calculate accordingly. Here, i and p represent data transmission band numbers and user numbers, respectively. Further, s (k, d, L) represents the cyclic shift amount caused by the sequence number k, the sequence length L, and the frequency offset, and the following equation

Relationship is established. c _p of the p-th user is, for example,

Can be calculated by P represents the number of pilots (users) multiplexed by the circular shift. In the case of FIG. 19, the circular shift amounts c _{1 to} c ₄ of users 1 to ₄ are

C ₁ = 0

c ₂ = [L / 4]

c ₃ = [2, L / 4] -s (k, d, L)

c ₄ = [3, L / 4] -s (k, d, L)

.

By the way, the channel estimation characteristics of both ends of the pilot transmission band are poor and the channel estimation characteristics of the intermediate portion are good, depending on the pilot signal reception system. In other words, the channel estimation accuracy is poor in the transmission bands of subcarriers 1 to 12 and 37 to 48 in FIG. 19, and the channel estimation accuracy is good in the transmission bands of subcarriers 13 to 24 and 25 to 36 in some cases.

Therefore, the transmission bands of intermediate subcarriers 13 to 24 and 25 to 36 are preferentially allocated to the user with poor radio path conditions, and the transmission bands of subcarriers 1 to 12 and 37 to 48 on both sides to users with good radio path conditions. Allocate In this way, there is no user whose channel estimation accuracy is extremely degraded. 19 shows an example of allocating users 2 and 3 to an intermediate transmission band.

As shown in Figs. 20 and 21, control (hopping control) can be performed so as to switch the transmission band allocated to each user for each frame. 20 is an explanatory diagram of allocation in odd frames, and FIG. 21 is an explanatory diagram of allocation in even frames.

In the odd-numbered frame, as shown in Fig. 20, subcarriers 1 to 12 and 37 to 48 on both sides are allocated to users 1 and 4, and intermediate subcarriers 13 to 24 and 25 to 36 are assigned to users 2 and 3, respectively. Allocate In the even-numbered frame, intermediate subcarriers 13 to 24 and 25 to 36 are allocated to user 4 and user 1 as shown in FIG. 21, and subcarriers 1 to 12 and 37 on both sides are assigned to user 3 and user 2. Allocate ~ 48. In the odd-numbered frames, the pilots of users 3 and 4 are multiplied by the frequency offset, and in the even-numbered frames, the pilots of the users 1 and 2 are multiplied by the frequency offset. In this way, there is no user whose channel estimation accuracy is extremely degraded.

Fig. 22 is a configuration diagram of the pilot generation unit in the case of hopping control, and the same reference numerals are given to the same parts as the pilot generation unit in Fig. 14A. The difference is that the frequency offset switching control unit 71 is added, and the other operations are the same.

The CAZAC series generating section 11 generates the indicated series length L and the CAZAC series ZC _k (n) of the series number as a pilot, and the cyclic shift section 12 includes c samples indicated by the CAZAC series ZC _k (n). The ZC _k (nc) obtained by the cyclic shift is input to the DFT unit 13. The DFT unit 13 of size N _TX (N _TX = L) performs a DFT operation on the input pilot ZC _k (nc) to generate a pilot DFT {ZC _k (nc)} in the frequency domain. The frequency offset switching control unit 71 determines whether or not to frequency offset based on the frequency offset amount d and the hopping pattern instructed by the transmission resource management unit 23. The subcarrier mapping unit 14 performs subcarrier mapping in accordance with whether or not to frequency offset. The IFFFT unit 15 having an N _FFT size (N _FFT = 128) performs an IDFT operation on the input subcarrier component, converts it into a pilot signal in the time domain, and inputs it to the frame generation unit 26.

ㆍ Effect of Invention

According to the present invention, it is possible to accurately estimate the channel of the data transmission subcarriers that deviate from the pilot transmission frequency band.

Further, according to the present invention, subcarriers allocated to each user are used as pilots of multiplexing users, even when a predetermined sequence (for example, the CAZAC series ZC _k (n)) having different amounts of cyclic shifts is used. The channel estimation can be performed with high accuracy.

In addition, according to the present invention, even if a pilot having multiple shifts in a predetermined sequence is used as a pilot for multiplexing users, the pilot of each user can be separated and a channel estimation can be performed by a simple method.

Further, according to the present invention, by allocating the intermediate portion of the pilot transmission band to a user with poor propagation path conditions, even a user with poor propagation path conditions can increase the channel estimation accuracy of the data transmission subcarrier of the user.

In addition, according to the present invention, by hopping the data transmission band allocated to the user in the middle part and the end part of the pilot transmission band, even a user with poor propagation path conditions can increase the channel estimation accuracy of the user's transmission data subcarrier. have.

Claims (3)

Each user terminal transmits a data signal to the base station using a frequency of a different data transmission band allocated from the base station, and transmits a pilot signal to the user terminal of the wireless communication system to multiplex the data signal to the base station. In
A receiver for receiving uplink resource information from a base station;
A pilot generator for generating a pilot according to the indication of the uplink resource information;
Transmitter for transmitting the pilot signal to the base station
Is provided, the pilot generation unit,
A CAZAC sequence generator that generates a Zadoff-Chu sequence as a pilot signal based on the resource information;
And a subcarrier mapping unit for mapping the series generated by copying the Zadoff-Chu sequence in a circular fashion. Each user terminal transmits a data signal to the base station using frequencies of different data transmission bands allocated from the base station, and multiplexes the pilot signal with the data signal to the base station. To
Receiving uplink resource information from a base station,
Generating a Zadoff-Chu sequence as a pilot signal based on the uplink resource information,
Map the series created by iteratively copying the Zadoff-Chu series,
And transmitting the mapped pilot signal. In the wireless communication system, each user terminal transmits a data signal to the base station using frequencies of different data transmission bands allocated from the base station, and transmits a pilot signal to the base station by multiplexing the data signal.
The base station comprises:
A first transmitter for transmitting uplink resource information to each of the user terminals;
Each of the user terminals,
A receiving unit which receives the uplink resource information;
A pilot generator for generating a pilot according to the indication of the uplink resource information;
Transmitter for transmitting the pilot signal to the base station
Is provided, the pilot generation unit,
A CAZAC sequence generator that generates a Zadoff-Chu sequence as a pilot signal based on the resource information;
And a subcarrier mapping unit for mapping the series generated by copying the Zadoff-Chu sequence in a circular fashion.

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